Pole-zero tracking frequency compensation for low dropout regulator

Most low dropout regulators (LDRs) have a limited of load current operating range due to stability problems. This paper proposes a new frequency compensation scheme for LDR to optimize the regulator performance over a wide load current range. By introducing a tracking zero to cancel out the regulator output pole, the frequency response of the feedback loop becomes load current independent. The open-loop DC gain is boosted up by a low frequency dominant pole, which increases the regulator accuracy. To demonstrate the feasibility of the proposed scheme, a LDR utilizing the new frequency compensation scheme is designed and fabricated using the TSMC 0.35μm digital CMOS process. Simulation results show that with output current from 0 μA to 100 mA, the bandwidth variation is only 2.3 times and the minimum DC gain is 72 dB. Measurement of the dynamic response matches well with simulation.